For wind turbines, in particular for wind turbine blades, stable and lightweight material is used. Specifically composite fibre components are used for the wind turbine blades due to the proper material characteristics.
Hence, the composite component made for example for the wind turbine blades comprises several reinforced fibre layers which form a stack. The composite component is often made by using a transfer moulding process. By using the transfer moulding process, the reinforced fibre layers are stacked above each other inside a mould. The mould defines a desired shape of the fibre components to be manufactured. After arranging the composite layers into the mould, from the opposed side of the mould a further mould, such as an inflatable bag, a vacuum membrane or a stiff mould, is attached. The stack is then pressed between the mould and the further mould. In a subsequent step, the stack and the single reinforced fibre layers are wetted and soaked with resin. Next, the soaked reinforced fibre layers of the stack are cured by a predefined temperature.
During manufacturing of the composite component, it has to be ensured that the single reinforced fibre layers are arranged in a correct position and thus form a geometrical conformity during the whole manufacturing process. In particular, the reinforced fibre layers have to be already fixed before the reinforced fibre layers are pressed and thus fixed between the respective moulds. Therefore, an underpressure or a vacuum is applied in order to soak the stack of reinforced fibre layers to one of the moulds. Thereby, the reinforced fibre layers are fixed to the respective mould.
In order to improve the vacuum fixing of the stack to the mould, a dense fibre material layer can be placed on a surface of the stack of composite layers. The dense fibre material layer has a low permeability to air in order to establish an underpressure between the mould surface and the sealed fibre material layer in order to fix the stack which is located between the sealed fibre material layer and the mould to the mould surface. Thus, the fibre material layup can be fixated, and thereby enable further movement without the risk of displacing the fibre layup.
EP 2 123 431 B1 discloses to apply a vacuum distribution layer at an inner surface of the mould. The vacuum distribution layer is connected to a vacuum pump such that the vacuum pump may suck the air through the vacuum distributing layer out of the stack.
On the one hand, it is desired that the top fibre layer of the stack, which layer forms a part of the structure reinforcement of the laminate, is of a conventional type and comprises a good resin wetting property and a good interlaminate shear strength relative to any adjacent structure elements such as shells, beams, etc. On the other hand, it is desired that the top fibre layer has a low permeability such that good vacuum properties are provided. In tendency, this top fibre layer with a low permeability to air generally comprises a relatively poor resin wetting property and a low interlaminate shear strength which would be normally desirable.
Furthermore, even with the relative low air permeability of the top fibre layer, an extremely large air flow is necessary to retain a sufficient pressure difference over the fibre layup for holding the stack to the mould surface, especially when moulding large parts like above described wind turbine blades.
Therefore, fixating the fibre layup with other means than a dense fibre surface material can be advantageous.